Field of the Disclosure
The present disclosure relates to an electrophotographic or electrostatic image forming apparatus, such as a copying machine, a printer, or a facsimile machine, and a developer container unit used by the image forming apparatus.
Description of the Related Art
Existing electrophotographic image forming apparatuses include a development device for forming a developed image by supplying a developer to an electrostatic latent image formed by scan-exposing an image bearing member. In addition, in recent years, many electrophotographic image forming apparatuses have included a process cartridge having a development device including a developer container unit having a developer, an image bearing member, and other process units (e.g., a charging member) integrated thereinto. By integrating a plurality of members into a process cartridge in this manner and allowing the process cartridge to be removable from the main body of the image forming apparatus, replenishment of developer and other maintenance work can be easily performed.
In such a process cartridge system, when the developer runs out, the user can replace the cartridge or refill the cartridge with new developer to form an image again. For this reason, in general, such image forming apparatuses include a unit for detecting consumption of the developer and warning the user of the replacement time, that is, a developer detecting unit.
As an example of such a developer detecting unit, Japanese Patent Laid-Open No. 2001-117346 describes a developer detecting unit that includes a pair consisting of an input electrode and an output electrode and that detects the amount of developer by measuring the capacitance between the two electrodes.
In addition, Japanese Patent Laid-Open No. 2003-248371 and Japanese Patent Laid-Open No. 2007-121646 describe a configuration in which a developer bearing member is regarded as an input electrode by applying an AC bias to a developer bearing member, and a capacitance detection member serving as an output electrode is disposed at a position facing the developer bearing member in a development device.
Each of Japanese Patent Laid-Open Nos. 2001-117346, 2003-248371, and 2007-121646 describes a technique for detecting the amount of developer by using a change in capacitance caused by a change in the amount of developer between a pair of electrodes.
To detect the current amount of developer, it is desirable that the amount of developer be detected even immediately before the developer completely runs out. Therefore, in a technique for detecting the amount of developer by using a change in capacitance, to easily detect a change in the amount of developer even when the amount of developer is small, it is desirable that the arrangement of the electrodes and the shape of members around the electrodes be optimized. However, in a configuration that enables a change in the amount of developer to be easily detected even when the amount of developer is small, it is sometimes difficult to accurately detect the amount of developer.